Means for converting electrical vibrations into sound waves



Jan 6, 1931. w. D. LA RUE 1,787,946

MEANS FOR CONVERTING ELECTRICAL VIBRATIONS INTO SOUND WAVES Filed May 14, 1925 5 Sheets-Sheet l g'rwewkoz W. D. LA RUE Jan 6, 1931.

. 1925 3 Sheets-Sheet Filed May 14 gnoento'c Jan' 6, 1931. w. D. LA RUE 1,787,946

MEANS FOR CONVERTING ELECTRICAL VIBRATIONS INTO SOUND WAVES Filed May 14, 1925 3 Sheets-Sheet 3 Patented Jan. e, 1931 UNITED STATES PATENT OFFICE WILLIAM D. LA RUE, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR T VICTOR TALK- ING MACHINE COMPANY, A CORPORATION OF NEW JERSEY MEANS FOR CONVERTING ELECTRICAL VIBRATIONS INTO SOUND WAVES Application filed May 14,

This. invention relates to means for converting electrical vibrations into sound waves,

and more particularly to a device employing a large sized diaphragm for use in combination with electrical circuits, such, for example, as radio receiving circuits, for converting electrical waves into sound waves of large volume.

It has heretofore been proposed to provide devices of this character with a diaphragm of such large size that the use of a horn or amplifier is unnecessary in order to produce the desired volume of sound. One of the difliculties that is encountered in the construction of a loud speaker employing such a large diaphragm results from the relatively large mass of the moving or vibrating parts. Usually these latter comprise a diaphragm of large diameter mechanically secured to anarmature or flapper. /Vhen producing loud notes, or when the period of the electrical vibrations approaches the natural period of one or all of the moving parts, the inertia of the latter so increases the amplitude of vibration that the flapper strikes the pole pieces and there is produced an objectionable rattling noise. If the air gap between the flapper and the pole pieces is increased to prevent the contacting of these elemen'ts,the sensitiveness of the device is greatly decreased.

An object of the present invention is to produce a loud speaker of the large diaphragm, hornless type which is so constructed as to overcome the above difficulties.

Another object of the present invention is to greatly reduce the mass attached to the flapper or armature without reducing the total vibrating area ofjthe device and without reducing the volume of sound emitted thereby.

Another object of the invention is to provide a device characterized by a pair of diaphrag'ms, one of which is immediately attached to the flapper or armature and the other of which is spaced at a distance from the first and is actuated by a calumn of air placed in motion by the vibration of the first diaphragm.

A further object is to provide a novel type 1925. Serial No. 30,300.

of diaphragm characterized by the fact that its length is greater than its width.

Another object is to provide a pleated diaphragm which is so formed that its pleats are of various lengths. X

Another object of the present invention is to provide a device of this character in combination with a mounting therefor, which mounting, due to its construction, materially aids in the volume and quality of the sound produced.

A still further object is to provide novel means for controlling the sensitiveness and volume of the device. These and other objects will appear more fully hereinafter.

Two forms that the inventive idea may assume are shown in the accompanying drawings, which drawings, however, are for purposes of illustration only and are not to be taken as defining the limits of the invention, reference being had to the appended claims for this purpose. In the drawings,

Fig. 1 is a front elevation of one embodiment of the present invention;

.Fig. 2 is a detail sectional view, somewhat enlarged and with parts broken away, taken on the line 2-2 of Fig. 1;

Fig. 3 is an enlarged detail sectional view taken on the line 3 3 of Fig. 2;

Fig. 4 is an enlarged sectional view taken on the line 44 of Fig. 9;

Figs. 5 and 6 are detail sectional views illustrating one manner in which the diaphragm may be mounted in the casing;

Figs. 7 and 8 are a longitudinal sectional view and a transverse sectional view respectively of one manner of forming the diaphragm center;

Fig. 9 is a front elevation of another em bodiment of the invention; and v Figs. 10 and 11 are detail views illustrating one form of means for securing the diaphragm to the casing.

Referring to the drawings wherein like reference characters refer to like parts throughout the several views, and particularly to Figs. 1 to 3, the device comprises a base or support 10 of any suitable character on which is mounted a casing 11. In orderto improve the quality and add to the volume of sound the casing 11 is preferably formed of wood but any other suitable material may be employed. The shape and size of the casing are not essential features, but in the preferred embodiment they conform to the outline of the particular diaphragm employed, which in this instance is diamond-shaped. Secured to the inner surface of the casing 11, closely adjacent the opposite ends thereof, are two inwardly extending frame members 12 to which are secured the outer edges of a pair of diaphragms 13 and 13a.

As will be pointed out more fully .hereinafter, various means may be employed for securing the diaphragms to the frame members. In the form shown, clamping strips 14 of wood, or other suitable material, secured to the framemembers 12, as by means of screws 15, constitute means for fixedly securing the diaphragms 13, 13a to the casing in operative position.

A variety of types of diaphragms may be employed in carrying out the present invention, but superior results are obtained by the use of a pleated diaphragm of the Lumiere type, formed of suitably coated material such as paper. In the preferred form of the invention, the length of the pleated diaphragms is greater than the width, or the same are so formed that the pleats are of various lengths. As illustrated the diaphragms, Which are mounted in parallel planes, are of the same size, form, and construction but it will be understood that this is not essential.

A pedestal 16 provided with clamping cars 17 is secured to the casing inany desired manner between the diaphragms 13, 13a. Mounted on this pedestaland secured in place by the cars 17 is an electrical unit of the telephone receiver type constructed in the usual, or any suitable, manner. Inthe form shown this unit comprises an outer casing 18 in which is slidably mounted an inner casing19. A magnet 20, pole pieces 21, and field coils 22 are mounted within this inner casing. Secured to the open end of the outercasing 18, in a plane substantially parallel to diaphragm 13, is an armature or flapper 23, the inner surface of the latter being separated by a narrow air gap from the ends of the pole pieces 21. The diaphragm 13 is mechanically 'connected in any desired. manner, as by means of the threaded member 24, to theflapper 23.

If desired, means may be provided, for

. varying the sensitiveness and volume of the loudspeaker. This is preferablydoneby adjusting the air gap between the armature, or.

flapper, and the pole pieces. In the form illustrated, an opening 25 is provided in the casing ,11 at any suitable point and -'thr.ough this opening extends the shank of a knurled adjusting knob 26. F ixedly attached to this knob is a. shaft 27 that may be secured at its inner end to a rod 28 rotatablv mounted in the outer casing 18 of the telephone unit. Preferably the rod 28 is 1'0- tatably supported at its opposite ends in the casing 18 in a plane between the closed end of the inner casing 19 and the rear or closed end of the outer casing 18. The rod 28 is provided intermediate the points where it passes through the casing 18 with an eccentric portion 28a which is engaged on the rear side thereof by a strap or stirrup 29 that is secured to the closed end of the inner casing 19 as by means of rivets 30. To insure engagement between the strap 29 and the eccentric portion 28a of the rod, a fiat spring 31 is preferably interposed between said strap and the rear end of the outer casing 18.

Qperation The variations of current in the electrical circuit (not illustrated) are transmitted by suitable lead wires 32 (Fig. 4) to the field coils 22 of the telephone unit. The varying magnetic field thus produced causes the flapper 23 and its connected diaphragm 13 to vibrate. The diaphragm 13a, which has no connection with the flapper 23, is dependent for its operation on the column of air, in the casing, set in motion by the vibrations of diaphragm 13. If it is desired to vary the loudness and sensitiveness of the device it is only necessary to rotate the knurled knob 26 which acts through the eccentric portion 28a of rod 28 and stirrup 29 to move the inner casing 19 and thereby increase or decrease the width of the air gap-between the poles 21.

and flapper 23. Various means may be employed for securing the diaphragmsto the surrounding casmg, and in Figs. 4, 5, and 6, there is disclosed means for lacing the diaphragms in operative position. In the form shown, a strip of felt 33 is folded lengthwise and glued-aroundthe peripheries of the 34a, which latter, in this instance, are circular, and are mounted in a cylindrical casing 35 provided with inwardly extending annular frame membersor rings 36 adjacent the opposite ends thereof. A number of hooks 37 are secured, at equal intervals, around the periphery of each diaphragm, to the felt strip 33, with the outer, curved end of the same extending radially beyond the outer edge of the strip and in the plane of the diaphragm. Spaced at equal intervals around the inner face of each ring 36, in staggered relation with the hooks 37, are a plurality of staples 38. A flexible lacing 39, which may be formedof waxed silk thread, alternately engages a hook and a staple and thus laces the diaphragm 'in operative position with the peripheries of'the'latterbearing against the inwardly curving ends of the rings 36. The tension of the lacing may be evened, if desired, by inserting one or more resilient members or springs 40 between adjacent ends of the lacing. In place of the lacing means, or the clampmg strips 14, a plurality of resilient members pleated diaphragms 34 and of the type illustrated in Figs. and 11, may be employed for operatively securing the diaphragm to its support. In the form shown, the periphery of the diaphragm 13a, which engages the frame member 12, may be engaged on the side opposite said frame member by a ring 44, of any suitable material,

, and secured in engagement with the ring 44, as by .means of a screw 45 which extends through the ring and diaphragm into the supporting member 12, are a plurality of resilient members 46 which are a-rcuate in shape, the radius of the are being substantially the same as the radius of the ring 44.. Each resilient member 4 6 is preferably curved inwardly at its opposite ends as at 46a, and the retaining member 45 passes through the central portion of the member, flexing said portion and rigidly clamping the same to the frame member 12. The resiliency of the member forces the inwardlycurved portions 46a into close engagement with the ring 44, thus clamping the diaphragm in operative position. Any suitable number of the clamping members 46 are employed and preferably these members are uniformly spaced around the periphery of the diaphragm, and if desired said members may be used without the'interposition of the ring- If desired, each of the diaphragms may be provided with a center for strengthening the same and to provide means for readily attaching the diaphragm to the flapper or armature. As illustrated, the diaphragm center comprises inner and outer concentric tubes 41, 42 that are formed of some light material such as paper. Suitably secured, as by means of glue, to the opposite ends of these cylinders, are the discs 43 having a diameter somewhat larger than the'diameter of the outer tube 42. The inner ends of the pleats of the diaphragm engage the outer periphery of the outer tube 42, and relative movement between the pleats and the center is prevented by thediscs 43 which constitute flanges.

lit will be apparent that there is provided a hornless loud speaker capable of producing superior results. A large vibrating or radiating surface, capable of producing a large volume of sound, is employed but the mass mechanically connected to the flapper is relatively small. Accordingly the desired sensit-iveness is secured, Without decrease in volume and Without danger being produced. The casing is ofsuch character as to increase the volume of sound and to improve the quality of the latter. Moreover, the device is compact and extremely pleasing inappearance. p

'lhense of a plurality of vibrating members tends to prevent the period of any one of the vibrating members from becoming dominant, since the natural period of one member tends to modify theperiods of the other movthe width of. the same.

of rattling noises,

of music. While only two forms of dia phragms, the diamond-sha' ed-and the circular, are illustrated in t e accompanying drawings, it will be understood that the invention is not limited thereto since a variety of shapes may be employed, but preferably, the length of the diaphragm is greater than Nor is the invention limited to the use of pleated diaphragms, or to the use of two similar diaphragms. It will also be understood that various other means may be employed for securing the diaphragms to the casing. Reference is therefore to be had to the appended claims for a. definition of the limits of the invention.

What is claimed is 1. A device of the class described comprising a casing, a diaphragm secured thereto; a second diaphragm secured to the casing at a distance from said'first named diaphragm, said casing and diaphragms forming an air chamber, and electrical means in said air chamber operatively connected to said firstnamed diaphragm only.

2. A device of the class described comprising a casing, a diaphragm secured at its outer edge to said casing, a second diaphragm constituting a sounding board secured to the casing at a distance from said first-named diaphragm, and electrical means between, said diaphragms and operatively secured to said first-named diaphragm only.

3. A device of the class described comprising a casing, a pair of diaphragms secured at their outer edges to said casing, and electrical means positioned in the air chamber formed by the diaphragms'and casing and opeiatively connected to one of said diaphragms on y. 1

4. A device of the class described comprising a casing, a diaphragm secured adjacent its outer edge to said casing, a second diaphragm secured to the casing at a distance from said first-named diaphragm, electrical means positioned between said diaphragms, and means for mechanically connecting said electrical means to the first-named diaphragm, said second-named diaphragm being actuated by the column of air set in mo tion by the vibrations of said first-named diaphragm. 1

5. A device of the class described comprising a casing, diaphragms mounted in the 0pposite ends of saidcasing, one of said diaphragms constituting a sounding board, and electrical means operatively secured to the other of said diaphragms, said diaphragms' opposite ends of said casing and vibrating into unconfined air, said diaphragms being sufiiciently large to generate sound Waves of substantially the desired ultimate volume,

and electrical means between said diaphragms and operatively secured to one of said diaphragms.

7 A device of the class described comprising a casing, pleated diaphragms mounted in the opposite ends of said casing, one of said diaphragms constituting a. sounding board, and electrical means operatively secured to the other of said diaphragms.

8. A. device of the class described comprising a casing, pleated diaphragms mounted in the opposite ends of said casing, and electrical means operatively secured to one of said diaphragms, said diaphragms and casing constituting a resonance chamber.

9. It loud speaker comprising a casing formed of resonant material, diaphragms secured adjacent the outer edges thereof to said casing, electrical means positioned in the resonance chamber formed by said casing and diaphragms, and means for mechanically connecting said electrical means to, one of said diaphragms.

10. A loud speaker comprising a casing formed of resonant material, pleated diaphragm secured to one end of said casing, electrical means operatively connected to said diaphragm for vibrating the same, and means vsecured to said casing for modifying the period of vibration of said firstnamed diaphragm;

ll. device of the class described comprising a casing, oblong diaphragm secured thereto, a second diaphragm secured to the casing in a plane parallel to the plane of the first-named diaphragm and at a distance therefrom, and electrical means operatively secured to said first-named diaphragm.

12. A device of the class described comprising a casing formed of resonant material, a diaphragm secured at its outer edge to said casing, a second diaphragm secured to the easing at a distance from said first-named diaphragm, and electrical means between said diaphragms and operatively secured to one of said diaphragms, .the other of said diaphragms bein actuated by the column of air set in motion lay the vibrations of said firstnamed diaphragm.

13. A device of the class described comprising a casing, a pair of pleated diaphragms operatively secured thereto, and electrical .means mounted between said diaphragms and operatively secured to one of the same.

14. A device of the class described comprising a casing formed of resonant material, a

pleated diaphragm secured to said casing, means constituting a sounding board secured to the casing, and means operatively secured to said diaphragm for vibrating the same.

15. A loud speaker comprising a casing, a diaphragm, means for securing said 'diaphragm at a plurality of points adjacent the outer edge thereof to said casing, a second diaphragm secured to the casing at a distance from said first-named diaphragm, and electrical means positioned in said casing between said casings and operatively secured to said first-named diaphragm only.

16. A device of the class described comprising a casing, a diaphragm, means for securing said diaphragm at a plurality of points adjacent the outer edge thereof to said casing, means constituting a soundingboard secured to the casing at a distance from said diaphragm, and electrical means positioned between said sounding board means and said diaphragm and operatively secured to said diaphragm.

1 Z. A device of the class described comprismg a casing formed of resonant material, lI1- Wardly projecting peripheral members secured to the caslng at the opposite ends thereof, a diaphragm operatively secured to one of said peripheral members, means constituting a sounding board having operative engagement With the other of said peripheral members, electrical means mounted in the casing between said diaphragm and sound board means, and means for operatively connecting said electrical. means to the diaphragm.

18. A device of the class described comprising a casing, a diaphragm peripherally mounted in said casing, the length of said diaphragm being greater than the Width thereof, and electrical means opera'tively secured to-said diaphragm.

iii. A loud speaker of the hornless type comprising supportin means, a diaphragm of oblong shape perip erally securedlio said \ineans, and means operatively secured to said diaphragm for vibrating the same.

20. A loud speaker of the hornless type comprising a casing, a pleated diaphragm peripherally mounted in said casing, the length of said diaphragm being greater than its Width, and means operatively secured to said diaphragm for vibrating the same.

2l. A loud speaker of the hornless type comprising a casing, a pleated diaphragm peripherally mounted in said casing, the pleats of the diaphragm being of various lengths, and electrical means for vibrating the diaphragm. 1

22. A loud speaker of the hornless-type comprising a-casing, a pleated diaphragm secured at its outer edge to said casing, the pleats of said diaphragm being of various lengths, and means mechanically secured to the diaphragm for vibrating the same.

lllll 1 combination of a casin her engaging the. periphery o phragm, and a plurality of clamps in engage 23. A loud speaker of the hornless type comprising a casing, a pair of diaphragms secured thereto, the length of said diaphragms being greater than the width thereof, and electrical means operatively secured to one of said diaphragms for vibrating the same.

24:. A loud speaker of the hornless type comprising a casing, a. pair of diaphragms secured to said casing in substantially parallelplanes, the length of said diaphragms being greater than the Width. thereof, and means operatively secured to one of said diaphragms for Vibrating the same.

25. A loud speaker of the hornless t pe comprising a casing, a pair of pleated iaphragms secured thereto, the pleats of said diaphragm being of various lengths, means operatively secured to one of said diaphragms for vibrating the same, the other of said diaphragms depending for its operation upon a column of air set in motion by the vibrations of said first-named diaphragm.

26. A diaphragm comprising a strip of flexible material folded into a series of pleats of varying lengths, the ends of said strip being united, and each of the pleats being under torsional tension.

27. A diaphragm for a loud speaker formed of pleated material, said pleats being of various lengths, each of said pleats being under torsional tension.

28. A diaphragm for a loud speaker formed of pleated material, said pleats being of various lengths, and a center comprising two concentric tubes, and discs secured to the opposite ends of the tubes, the outer one of said tubes being engaged by the inner ends of the pleats.

29. In a device of the class described, the combination of a casing, a diaphra a memthe diament with said member for securing the diaphragm to said casing.

30. In a device of the class described, the combination of a casing, a diaphragm, and a plurality of arcuate members the diaphragm to the casing.

31. In a device of the class described, the

a diaphragm, and a plurality of clamps in engagement with said diaphragm for securing the same to said casing.

32. In a device of the class described, the combination of a casing, a diaphragm, and a plurality of resilient clamps in engagement with said diaphragm for securing the same to said casing.-

33. In a device of the class described, the

combination of a casing, a diaphragm, and i a plurality of resilient arcuate members for securing the diaphragm to the casing.

34. In a device of the class described, the combination of a casing, a diaphragm, and

for securing specification.

' WILLIAM D. LA RUE. 

